Hitherto, magnesium chloride and magnesium alkoxides have been widely used as a support material without being milled in the field of catalysts for olefin polymerization, specifically the homopolymerization or copolymerization of α-olefin such as ethylene and propylen. This may improve the catalyst activity and the morphology of polymer powder.
For example, for improving an obtained polymer in morphology including particle size, form, etc., there are known a method in which a magnesium compound is supported on an inorganic oxide such as silica (JP-A-S63-280707) and a method in which a magnesium compound once dissolved in a solvent such as an alcohol is precipitated again and the precipitate is used (JP-A-S58-000811). However, these methods include very complicated steps, since they require the procedures of supporting, dissolving and precipitating a magnesium compound. Further, these methods have a defect in that the catalyst is poor in performance stability.
The method of using as a support of catalysts a magnesium compound obtained by reacting metal magnesium, an alcohol such as ethanol and a certain amount of halogen (JP-A-H4-130107) has been developed. However, it has a problem in the point that the catalyst activity and the apparent density of the polymer powder obtained depends on the conditions.
In order to improve a polymerization activity and an appearance of film in ethylene polymerization, the method of using a support such as magnesium alkoxide pulverized mechanically (JP-A-H9-194522) has been disclosed.
However, the pulverization of a support causes increase in amount of fine powder contained in polymer powder, which reflects the properties of support particles, and bad powder form. A converting line may be blocked due to the increase in amount of fine powder. The flowability of powder may be lowered due to the bad powder form, thereby letting reactor operation unstable. Further the polymerization activity and controllability of molecular weight may be unsatisfactory.
In view of the above-mentioned problems, a purpose of the invention is to provide a magnesium compound which exhibits high activity without decrease of performances such as stereoregularity and appearance of film (fish-eye), are excellent in control of molecular weight and can give an olefin polymer excellent in apparent density; a solid catalyst component; a catalyst for olefin polymerization; and a method of producing an olefin polymer.